Retroplayer

BTW, it sounds like you appreciate mechanisms as much as I do. I always observe how machines work and am enchanted especially with automata. I am not a mechanical engineer (an electrical engineer actually), just lots and lots of observation.

I do have a cool book that I can recommend: Mechanisms and Mechanical Devices Sourcebook

Thousands of different mechanisms diagrammed and explained. Maybe I will find some pictures in my copy that will help.

Retroplayer

Saved the link to my favorites. Thanks for sharing it! I could picture that mechanism in my head because I have seen it before on coil-widing machines, but couldn't remember how it reversed direction.

The only limitation to it is that the OP mentions variable widths. This could be solved with a square shaft that he can slide on different lengths of these at different points depending on how many piles he is trying to make and how wide.

jabbado

The only limitation to it is that the OP mentions variable widths. This could be solved with a square shaft that he can slide on different lengths of these at different points depending on how many piles he is trying to make and how wide.

I think it's can be simpler than that. Just have a long shaft with the spirals milled all along it. Then you put "stops" along the shaft where required. Bit hard for me to explain but if the stops are just either side of a "X" part of the spirals it basically turns that location into the end of the shaft and causes the cam follower to reverse at that point.

PeterH

I think it's can be simpler than that. Just have a long shaft with the spirals milled all along it. Then you put "stops" along the shaft where required. Bit hard for me to explain but if the stops are just either side of a "X" part of the spirals it basically turns that location into the end of the shaft and causes the cam follower to reverse at that point.

If you have spirals cut in both directions, there will be a cross-over every time they meet. How do you ensure that the follower keeps going across these rather than reversing?

PeterH

If I am understanding him right, the stops have the < and > groove to them to redirect the follower into the other track.

Yes, but it's not the ends I'm asking about - it's the crossing points in the middle. When the grooves cross what's to stop the follower from changing direction? At the end of the track there's only one option and the follower has to change direction. But at the intermediate crossing points, there are two options and nothing to prevent the follower from taking either of them.

If I am understanding him right, the stops have the < and > groove to them to redirect the follower into the other track.

Yes, but it's not the ends I'm asking about - it's the crossing points in the middle. When the grooves cross what's to stop the follower from changing direction? At the end of the track there's only one option and the follower has to change direction. But at the intermediate crossing points, there are two options and nothing to prevent the follower from taking either of them.

oh... the follower is long enough that it touches both sides even at the crossing points so it stays on the track it is on. And the tapers on the end of the follower are designed to allow it to flip angle at the ends. The shape of the follower is actually the most important part of the mechanism.

PeterH

oh... the follower is long enough that it touches both sides even at the crossing points so it stays on the track it is on. And the tapers on the end of the follower are designed to allow it to flip angle at the ends. The shape of the follower is actually the most important part of the mechanism.

I imagine something like that would be required, but I'm struggling to follow how that would enable you to adjust the end points i.e. have a spool that has a crossing point that can optionally be 'blocked off' to make the follower reverse at that point. If the shape of the groove and follower make it possible for the follower to reverse at that point, what prevents it from reversing even when the crossing is not 'blocked off' iyswim? It seems to me that for this to work, the turning points at the ends need to be a different shape to the crossing points in the middle. Maybe there's a devious way round that, but I can't figure it.

Retroplayer

Because of the length and shape of the follower, it cannot follow the cross tracks. It requires the leading edge of the follower to bump against an edge to toggle it in the other direction. The end stops provide this edge that bumps it and toggles it. Notice the taper on the edges. They touch nothing at all while following the track until they hit the end points.